Plant Essential Oils as Active Antimicrobial Agents

Essential oils derived from plants have been recognized for decades to exhibit biological activities, including antioxidant, anticancer, and antimicrobial attributes. Antimicrobial activities of these natural plant materials have been intensively explored in recent years, mainly in response to the overwhelming concern of consumers over the safety of synthetic food additives. Gram-negative organisms are believed to be slightly less sensitive to essential oils than Gram-positive bacteria. Generally, a higher concentration is required to obtain the same efficacy in foods than in synthetic media. The combinations of different types of essential oils or with other food additives have been found to potentially exhibit synergistic if not additive effects. This suggests a cost-efficient and wholesome alternative to both food industry and consumers, at the same time adhering to the hurdle technology in inhibiting proliferation of foodborne pathogens. This review aims to examine the conventional methods commonly used for assessment of antimicrobial activities of essential oils and phytochemicals, the use of these substances as antimicrobials in food products, factors that affect their efficacy, synergism between components or with available food preservatives as well as the challenges and future directions of using essential oils and phytochemicals as natural food preservatives.     

Essential oils as natural preservatives for bakery products: Understanding the mechanisms of action,recent findings,and applications

Abstract

Bakery products, as an important part of a healthy diet, are characterized by their limited shelf-life. Microbiological spoilage of these products not only affects the quality characteristics and result in the economic loss but also threatens consumer’s health. Incorporation of chemical preservatives, as one of the most conventional preserving techniques, lost its popularity due to the increasing consumer’s health awareness. Therefore, the bakery industry is seeking alternatives to harmful antimicrobial agents that can be accepted by health-conscious customers. In this regard, essential oils have been previously used as either a part of product ingredient or a part of the packaging system. Therefore, the antimicrobial aspect of essential oils and their ability in delaying the microbiological spoilage of bakery products have been reviewed. Several types of essential oils, including thyme, cinnamon, oregano, and lemongrass, can inhibit the growth of harmful microorganisms in bakery products, resulting in a product with extended shelf-life and enhanced safety. Research revealed that several bioactive compounds are involved in the antimicrobial activity of essential oils. However, some limitations, such as the possible negative effects of essential oils on sensory parameters, may limit their applications, especially in high concentrations. In this case, they can be used in combination with other preservation techniques such as using appropriate packaging materials. Further research regarding the commercial production of the bakery products formulated with essential oils is required in this area.     

Use of essential oils and phytochemicals against the mycotoxins producing fungi for shelf-life enhancement and food preservation

Mycotoxin-producing fungi are a significant source of crop and food contamination, posing a significant threat to global food safety and security. Essential oils, plant extracts and phytochemicals have emerged as green preservatives to extend the shelf-life of foods due to their unique antimicrobial properties. Unlike conventional synthetic preservatives, they are a sustainable and safe way to preserve food with no or little harmful effects on the environment. Use of nanoformulations containing essential oils and phytochemicals offer enormous potential as a mitigation strategy to lower mycotoxin contamination incidences in food and crop with enhanced release behaviour to efficiently transport them to the target location for a rapid reaction without much impact from environmental variables. Hence, this review overviews various essential oils and phytochemicals utilized through nanoformulations to control the mycotoxigenic fungi, probable mechanism of actions involved as well as emerging mycotoxins and associated safety concerns to ensure food sustainability.     

Essential Oils as Natural Food Antimicrobial Agents: A Review

Food-borne illnesses pose a real scourge in the present scenario as the consumerism of packaged food has increased to a great extend. Pathogens entering the packaged foods may survive longer, which needs a check. Antimicrobial agents either alone or in combination are added to the food or packaging materials for this purpose. Exploiting the antimicrobial property, essential oils are considered as a “natural” remedy to this problem other than its flavoring property instead of using synthetic agents. The essential oils are well known for its antibacterial, antiviral, antimycotic, antiparasitic, and antioxidant properties due to the presence of phenolic functional group. Gram-positive organisms are found more susceptible to the action of the essential oils. Essential oils improve the shelf-life of packaged products, control the microbial growth, and unriddle the consumer concerns regarding the use of chemical preservatives. This review is intended to provide an overview of the essential oils and their role as natural antimicrobial agents in the food industry.     

植物精油在水产品保鲜中的研究进展

水产品产后腐败损失及其导致的食品安全问题仍然是我国水产品加工业发展的制约因素。植物精油是从芳香植物中提取的具有挥发性及芳香气味的次生代谢产物,具有抗菌和抗氧化等功能,是一种极具潜力的水产品保鲜剂。本文对目前植物精油在水产品保鲜中的应用现状、保鲜效果、对产品风味影响及其食用安全性进行了综述。     

Use of Cymbopogon citratus essential oil in food preservation: Recent advances and future perspectives

The economic burdens and health implications of food spoilage are increasing. Contamination of food sources by fungi, bacteria, yeast, nematodes, insects, and rodents remains a major public health concern. Research has focused on developing safer natural products and innovations to meet consumers' acceptance as alternatives to synthetic food preservatives. Many recent novel preservative techniques and applications of both natural and synthetic origin continue to proliferate in food and chemical industries. In particular, some essential oils of plant origin are potent food preservatives and are thus attractive alternatives to synthetic preservatives. This paper provides an overview of recent advances and future prospects in assessing the efficacy of the use of Cymbopogon citratus (lemongrass) essential oil in food preservation. The possible mechanisms of action and toxicological profile as well as evidence for or against the use of this essential oil as an alternative to synthetic food preservatives in domestic and industrial applications are discussed.     

Control of Pathogenic and Spoilage Microorganisms in Fresh‐cut Fruits and Fruit Juices by Traditional and Alternative Natural Antimicrobials

ABSTRACT: Traditional antimicrobials have been extensively used for many years. However, consumers are currently demanding wholesome, fresh‐like, and safe foods without addition of chemically synthesized preservatives. The application of novel natural antimicrobials to assure safety of fresh‐cut fruits and unpasteurized juices while preventing quality loss is a promising alternative. The effectiveness of these natural substances added to fruit derivatives has been studied by different researchers. Antimicrobials of animal (lactoperoxidase, lysozyme, and chitosan), plant (essential oils, aldehydes, esters, herbs, and spices), and microbial origin (nisin) can be used to effectively reduce pathogenic and spoilage microorganisms in fresh‐cut fruits and fruit juices. Nevertheless, the use of these compounds at a commercial level is still limited due to several factors such as impact on sensory attributes or, in some cases, regulatory issues concerning their use. Therefore, extensive research on the effects of each antimicrobial on food sensory characteristics is still needed so that antimicrobial substances of natural origin can be regarded as feasible alternatives to synthetic ones.     

Flower Extracts and Their Essential Oils as Potential Antimicrobial Agents for Food Uses and Pharmaceutical Applications

Abstract: Plants with potential therapeutic value have been used from time immemorial to cure various ailments and infectious diseases. Secondary metabolites or the bioactive compounds (phytochemicals) present in plants have been reported to be accountable for various observed biological activities. Consumer awareness of the possible side effects of using chemical‐based antimicrobial agents has forced researchers to identify and explore natural plant‐based antimicrobial agents (or preservatives) that are toxicologically safe, especially when used in food applications. Of late, scientific evidence has been provided on the potential antimicrobial activities exhibited by certain traditionally used flower extracts or their essential oils (edible and wild). This review focuses on providing and updating available information on the antimicrobial activities exhibited by flowers, which are envisaged to find potential applications as natural preservatives for foods or applications in the pharmaceutical industries to develop new and economical herbal‐based products for treating various diseases.     

Plant extracts for the control of bacterial growth: efficacy, stability and safety issues for food application

The microbial safety of foods continues to be a major concern to consumers, regulatory agencies and food industries throughout the world. Many food preservation strategies have been used traditionally for the control of microbial spoilage in foods but the contamination of food and spoilage by microorganisms is a problem yet to be controlled adequately. Although synthetic antimicrobials are approved in many countries, the recent trend has been for use of natural preservatives, which necessitates the exploration of alternative sources of safe, effective and acceptable natural preservatives. Plants contain innumerable constituents and are valuable sources of new and biologically active molecules possessing antimicrobial properties. Plants extracts either as standardized extracts or as a source of pure compounds provide unlimited opportunities for control of microbial growth owing to their chemical diversity. Many plant extracts possess antimicrobial activity against a range of bacteria, yeast and molds, but the variations in quality and quantity of their bioactive constituents is the major detriments in their food use. Further, phytochemicals added to foods may be lost by various processing techniques. Several plant extracts or purified compounds intended for food use have been consumed by humans for thousands of years, but typical toxicological information is not available for them. Although international guidelines exist for the safety evaluation of food additives, owing to problems in standardization of plant extracts, typical toxicological values have not been assigned to them. Development of cost effective isolation procedures that yield standardized extracts as well as safety and toxicology evaluation of these antimicrobials requires a deeper investigation.     

Recent developments in the application of seaweeds or seaweed extracts as a means for enhancing the safety and quality attributes of foods

The production of rancid flavors and odors due to oxidative stress in foods can lead to a reduction in the sensory attributes, nutritional quality and food safety. Due to consumer demands, interest has been generated in searching plant products for natural “green” additives. Extracts from macroalgae or seaweeds are rich in polyphenolic compounds which have well documented antioxidant properties. They also have antimicrobial activities against major food spoilage and food pathogenic micro-organisms. Thus, possibility of seaweeds being added to foods as a source of antioxidant and antimicrobial is the main focus of this communication. In addition, seaweeds are also rich in dietary minerals specially sodium, potassium, iodine and fibers. Another potential area where the use of seaweed is gaining importance is regarding their addition for improving the textural properties of food products which is also extensively reviewed in this paper.

Industrial relevance

The trend towards the use of “natural green” plant extracts in various food and beverages in the food industry is gaining momentum. Seaweed, being a rich source of structurally diverse bioactive compounds with valuable nutraceutical properties, can be used as an ingredient to supplement food with functional compounds. Interest in the application of such compounds as natural antioxidants, antimicrobials or texturing agents in different food products is greater than ever. The addition of seaweeds or their extracts to food products will reduce the utilization of chemical preservatives, which will fulfill the industry as well as consumer demands for “green” products. In addition, the current status and the future projections in the functional effects of seaweeds as a means to improve the fiber content and reduce the salt content of food products, which will be of significant importance to the meat industry, is also discussed.     

Essential Oils: Extraction,Bioactivities, and Their Uses for Food Preservation

Essential oils are concentrated liquids of complex mixtures of volatile compounds and can be extracted from several plant organs. Essential oils are a good source of several bioactive compounds, which possess antioxidative and antimicrobial properties. In addition, some essential oils have been used as medicine. Furthermore, the uses of essential oils have received increasing attention as the natural additives for the shelf‐life extension of food products, due to the risk in using synthetic preservatives. Essential oils can be incorporated into packaging, in which they can provide multifunctions termed “active or smart packaging.” Those essential oils are able to modify the matrix of packaging materials, thereby rendering the improved properties. This review covers up‐to‐date literatures on essential oils including sources, chemical composition, extraction methods, bioactivities, and their applications, particularly with the emphasis on preservation and the shelf‐life extension of food products.     

Essential oils as biopreservatives: different methods for the technological application in lettuce leaves

Investigations were carried out to assess the efficiency of 3 essential oils, clove, tea tree, and rosemary, as natural preservatives during the postharvest of lettuce leaves. The effect of different concentration (1 and 0.5 MIC) of plant essential oils applied in 3 forms (spray, immersion, and capsules) was studied on lettuce leaves. The evolution of different microbial populations was evaluated during refrigerated storage. The application forms of the biopreservatives were shown to be an important factor in determining the effectiveness of the essential oils. Clove and tea tree essential oils at 1 MIC and applied embedded in lactose capsules presented a significant inhibition on mesophilic, psicrotrophic, and coliforms populations, while rosemary in none of the 3 technological applications forms exerted inhibitory effect on all microbial populations evaluated. Essential oils (at 0.5 MIC) applied by spray, immersion, and embedded in lactose capsules exerted lower inhibitory effects, with respect to 1 MIC, on the different microbial populations present on lettuce leaves. At the end of the storage (7 d), lettuce samples treated with tea tree, clove, and rosemary (at 1 and 0.5 MIC) by spray were the only organoleptically acceptable. It is concluded that clove and tea tree essential oils can control different microbial population present in lettuce. Practical Application: The exploration of naturally occurring antimicrobials in food preservation receives increasing attention due to consumer awareness of natural food products. Biopreservatives are useful in extending the shelf life of foods, reducing or eliminating pathogenic bacteria and increasing overall quality of food products. The effectiveness of essential oil application in foods is the result of factor associations such as applications forms, concentration applied, the way of action, storage temperatures. The application methods (spray, immersion, and embedded in lactose capsules) and the concentration of essential oils have been shown to be important factors in determining the effectiveness of these biopreservatives. The oil concentrations required to produce a certain level of inhibition in actual foods could be questionable due to the organoleptic impact. However, these novel natural preservatives in combination with other factors in obstacle technologies are an alternative to control the pathogen growth minimizing undesirable changes in organoleptic characteristics.     

芳香精油在食品保藏中的应用性研究进展

芳香精油是重要的植物次生代谢物,药食应用历史悠久,因其多方面的生物活性,已引起人们对其在食品保藏领域替代化学防腐剂的极大兴趣。文中概述了芳香精油及其成分在采后果蔬、预切果蔬片、肉制品、乳制品和水产品等食品保鲜和贮藏领域中应用性和安全性研究的最新研究进展。许多研究表明,牛至、丁香、罗勒、胡荽、肉桂、百里香、薄荷、迷迭香、芥茉、芫荽、红根草等芳香精油以及丁子香酚、香芹酚、肉桂酸、己醛、草蒿脑、麝香草酚、香芹酮、肉桂醛、柠檬醛、香叶醇等单体成分具有优良的抗食源性腐败菌和致病菌活性。通过与食品生产前处理工艺、气调包装、配方优化等手段的结合,一些芳香精油及其成分显示出天然食品保藏剂良好的商用价值。     

Antimicrobial activity of whey protein isolate edible films with essential oils against food spoilers and foodborne pathogens

The use of antimicrobial edible film is proposed as a means of improving food safety and extending the shelf-life of food systems by controlling the release of antimicrobials on food surfaces. In this work we first selected and studied 8 different essential oils (EOs) from plants, namely, oregano, clove, tea tree, coriander, mastic thyme, laurel, rosemary, and sage as natural antimicrobials against 2 gram-positive bacteria (Listeria innocua and Staphylococcus aureus) and 2 gram-negative bacteria (Salmonella enteritidis and Pseudomona fragi) by using the agar disk diffusion method. EOs from oregano, clove, and tea tree produced the largest surfaces of inhibition against the growth of the 4 bacterial strains tested. Second and following the assessment of compatibility, stable antimicrobial edible films based on whey protein isolate (WPI) with increasing concentrations (0.5% to 9%) of the 8 EOs were developed and tested for antimicrobial activity against the same gram-positive and gram-negative bacteria. WPI-edible films incorporating oregano or clove EO were found to have the most intense inhibitory effect of microbial growth. The bacterial strain gram-negative P. fragi presented the less susceptibility to the effect of those films. Moreover, only the edible films based on these 2 EOs were active against all 4 studied microorganisms. On the other hand, the edible films incorporating tea tree, coriander, mastic thyme, laurel, rosemary, or sage EOs even at high concentrations (7% to 9%) did not cause any antimicrobial effect against the pathogens S. aureus or S. enteritidis. PRACTICAL APPLICATION: Potential applications of this technology can introduce direct benefits to the food industry by improving safety and microbial product quality. The results of this research have direct application in the food industry with potential applications in various foodstuffs, including meat and poultry products where the control of spoilage bacteria such as P. fragi throughout their chilled storage or the improvement of food safety by controlling pathogens such as S. enteritidis are topics of particular interest for the industry.     

植物源精油的抑菌机制及其在食品保鲜包装中的应用进展

随着人们生活水平的不断提高,对饮食结构的要求随之提高,食品安全问题已成为关注焦点之一。而目前在食品生产与包装中使用最广泛的化学防腐剂已不足以满足人们对于安全、健康、绿色的需求。因此,植物源精油的抗菌保鲜方式因其显著的抗菌效果与无毒无残留的特性受到越来越多的关注,其在食品保鲜上的应用已成为研究热点。本文就植物源精油的抑菌活性、作用机理及其在食品保鲜中的应用进行综述,以期为天然食品防腐保鲜剂的开发及植物源精油在食品保鲜中的应用提供参考。     

植物精油在包装领域的研究应用进展

近年来,人们对在食品中使用天然抗菌剂代替化学防腐剂的兴趣日益增加。就此而言,精油这种具有挥发性且安全无害的天然植物次生代谢产物无疑将会在食品功能包装领域得到广泛的研究和应用。目前大量研究表明,加入精油后的食品包装可增强食品的抗菌和抗氧化活性、减缓酶促褐变、改变食品周围的气体环境以及水蒸气渗透等效果。本文特以此为切入点,介绍了植物精油的生物学效应,以及植物精油作为一种活性成分在当前的研究、开发和应用。因此,开发植物精油用作生物基食品包装,将精油本身与纳米乳液纳入活性或智能包装中,加入到产品或包装表面涂层、充入气调包装中、在包装内添加小袋和加入到包装膜上等,无疑可以用来改善产品品质的影响,减少食品行业的浪费。该研究还涵盖了植物精油在食品包装中的常见技术应用,如可降解的生物薄膜、微胶囊包埋、纳米乳液和静电纺丝等,以期为植物精油在包装领域的应用提供新途径。     

Recent advances in biobased and biodegradable polymer nanocomposites,nanoparticles, and natural antioxidants for antibacterial and antioxidant food packaging applications

Inorganic nanoparticles (NPs) and natural antioxidant compounds are an emerging trend in the food industry. Incorporating these substances in biobased and biodegradable matrices as polysaccharides (e.g., starch, cellulose, and chitosan) and proteins has highlighted the potential in active food packaging applications due to more significant antimicrobial, antioxidant, UV blocking, oxygen scavenging, water vapor permeability effects, and low environmental impact. In recent years, the migration of metal NPs and metal oxides in food contact packaging and their toxicological potential have raised concerns about the safety of the nanomaterials. In this review, we provide a comprehensive overview of the main biobased and biodegradable polymer nanocomposites, inorganic NPs, natural antioxidants, and their potential use in active food packaging. The intrinsic properties of NPs and natural antioxidant actives in packaging materials are evaluated to extend shelf-life, safety, and food quality. Toxicological and safety aspects of inorganic NPs are highlighted to understand the current controversy on applying some nanomaterials in food packaging. The synergism of inorganic NPs and plant-derived natural antioxidant actives (e.g., vitamins, polyphenols, and carotenoids) and essential oils (EOs) potentiated the antibacterial and antioxidant properties of biodegradable nanocomposite films. Biodegradable packaging films based on green NPs—this is biosynthesized from plant extracts–showed suitable mechanical and barrier properties and had a lower environmental impact and offered efficient food protection. Furthermore, AgNPs and TiO₂ NPs released metal ions from packaging into contents insufficiently to cause harm to human cells, which could be helpful to understanding critical gaps and provide progress in the packaging field.     

抗氧化天然植物提取物及其在肉品中的应用研究进展

在各类肉品的生产和加工过程中,食品防腐添加剂对于保持产品营养特性和安全性必不可少。然而,人们期待肉品中所添加的成分尽可能源自天然产物,因此寻找可替代食品防腐抗氧化添加剂功能的天然提取物越来越受到关注。现有研究的抗氧化天然提取物来源于蔬菜、水果、香辛料、草本和种子等,主要作用是抑制脂质氧化、酸败,也可在一定程度上抑制微生物生长,应用于各类肉制品中,以有效延长其保质期,甚至还具有其他的功能特性。本文对抗氧化天然提取物的来源、萃取、氧化反应、功能性表现,特别是在各类肉品中的应用进行综述,以期为健康、安全、具有较长保质期和稳定货架期肉品的加工提供借鉴。     

植物源天然防腐剂应用及抑菌机理研究现状

植物源天然防腐剂是一类从植物中提取出来的抑菌物质,天然绿色,是理想的抑菌防腐资源。我国食品行业正朝着营养健康的方向发展,消费者对食品安全的追求,都使得天然防腐剂的需求不断提升。该文综述了植物源天然防腐剂在动物性、水产、植物性和面制食品领域的应用现状及其抑菌机理,以期为植物源天然防腐剂在食品工业中的广泛应用提供思路。